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Page 1 of 1 <br /> v � <br /> Vicki McCartney [EH] <br /> From: Vicki McCartney [EH] <br /> Sent: Thursday, June 09, 2011 3:21 PM <br /> To: jeanne.homsey@atcassociates.com' <br /> Subject: Former Thiemann's Service Station <br /> Good afternoon, Jeanne. <br /> I have confirmation from Jim Barton of the California Regional Water Quality Control Board Central Valley <br /> Region that soil data is not to be used in the Johnson and Ettinger(J&E) Model to evaluate health risks from <br /> subsurface vapor intrusion into buildings. Only soil gas results should be used in the the J&E Model. Also, in the <br /> Department of Toxic Substances Control California Environmental Protection Agency document Interim Final <br /> Guidance for the Evaluation and Mitigation of Subsurface Vapor Intrusion to Indoor Air, date December 15, 2004, <br /> it states that the "Maximum contaminant concentrations should be used"when performing a preliminary screening <br /> evaluation for vapor intrusion. This means that you should not use averages when entering concentrations into <br /> the J&E Model. <br /> That said, the J&E Model that you submitted in Closure Summary Report, dated 13 December 2010 for the <br /> Former Thiemann's Service Station site located at 106 Second Street in Ripon is not acceptable. However, since <br /> ATC Associates Inc. (ATC) did collect soil gas samples and the reported soil gas concentrations were below the <br /> screening levels, there is no need to resubmit the J&E Model using the highest soil gas concentrations. <br /> As I mentioned in a previous email dated 23 May 2011, please submit an estimate of the time it will take before <br /> the groundwater contaminant concentrations at the Thiemann's site will return to water quality objectives. <br /> Also, ATC must address soil concentration results for contaminants of concern that exceed the ESLs for gross <br /> contamination and direct exposure. By this I mean that ATC must explain why high contaminant concentrations <br /> found in soil samples will not pose a health risk. ATC submitted Addendum to ATC's Additional Subsurface <br /> Investigation for Former Thiemann's Service Station (Addendum), dated 23 September 2010. In the Addendum, <br /> ATC presents the soil concentrations that exceed the ESLs. (Please note that the ESL for benzene is 0.044 <br /> mg/kg, not 0.0044 mg/kg.) Now ATC must take that information and present a case why ATC believes the soil <br /> contamination will not pose a significant threat to human health or to the environment. For example, is the <br /> surface either concrete or asphalt, creating a barrier? Is the structure on site built on concrete slab creating a <br /> barrier for potential exposure? Were the soil samples detected with high petroleum hydrocarbon contaminant <br /> concentrations collected at depths unlikely to be exposed to the general public? Where were the soil samples <br /> collected in relation to the building and how will that affect everything? What is the likelihood that this site will be <br /> used for the construction of residential structures? I think you get the idea. <br /> Jeanne, ATC can submit this as an attachment in an email to me. Keep it simple and address only the issues that <br /> I have requested. <br /> Thank you, Jeanne. <br /> Vicki McCartney, Senior REHS <br /> San Joaquin.County <br /> Environmental Health Department <br /> 600 East Main Street <br /> Stockton,California 95202 <br /> Phone: (209)468-9852 <br /> Fax: (209)468-3433 <br /> Email: vmccartney(a?sjcehd.com <br /> 6/9/2011 <br />